Question

1. a photo shows an ice cube wrapped in foil, one in paper, one in plastic, and one uncovered. what is the independent variable?

a) the wrapping material
b) the size of the ice cube
c) the time measured
d) the surface they are placed on

1. a bar graph shows reaction times for students with no caffeine, 50 mg caffeine, and 100 mg caffeine. the dependent variable is:

a) number of students
b) reaction time
c) amount of caffeine
d) type of test

1. a student uses a thermometer and records: 25°c, 27°c, 30°c. this type of data is:

a) qualitative
b) quantitative
c) hypothetical
d) constant

1. a microscope image shows bacterial growth in four petri dishes: three with antibiotics and one without. the dish without antibiotics is the:

a) constant
b) control group
c) independent variable
d) dependent variable

Explanation:

Question 20:

The independent variable is what is changed in an experiment. Here, the type of wrapping material around the ice - cube is being changed, so it is the independent variable.

Question 21:

The dependent variable is what is being measured. In the bar - graph, reaction time is being measured as the amount of caffeine changes, so reaction time is the dependent variable.

Question 22:

The data recorded as temperatures ($25^{\circ}C$, $27^{\circ}C$, $30^{\circ}C$) are numerical values, so this is quantitative data.

Question 23:

In an experiment, the group without the treatment (in this case, the petri - dish without antibiotics) is the control group.

Answer:

1. A. The wrapping material
2. B. Reaction time
3. B. Quantitative
4. B. Control group